Influence of current transformers on the measurement of harmonic active power

The harmonic active power is a useful power quality quantity. For example it is used in many algorithms for the detection of the harmonic source in a complex electrical network. The highest uncertainties in such kind of measurements are introduced by the transducers. In the paper is presented an experimental analysis of the effects of current transformer in the measurement of harmonic power. It is concluded that large phase angle errors can cause as larger errors as the phase shift between harmonic voltage and harmonic current get close to ±90. Moreover if such measurements are used to determine the power flow direction, i.e., if a load or consumer pollutes or is polluted, even high accuracy class CTs may yield unsatisfactory results.